On a related note, it���s well worth reading ���Myths about /dev/urandom��� (http://www.2uo.de/myths-about-urandom/ ) as well as the pages it references. Linux���s use of the blocking-when-entropy-is-low /dev/random is somewhat confusing, and at times very frustrating - and for the vast majority of use cases, completely unnecessary. 

( I raise this only because the quoted article above still suggests that you need to keep the ���entropy pool topped off at full���, which is perpetuating the myth)

And amusingly, Aaron Toponce (who owns pthree.org above) was the author of the other great article I read on how people misunderstand /dev/urandom: https://pthree.org/2014/07/21/the-linux-random-number-generator/.  Also worth a read. (And yet,) he still suggests that ���topping off��� /dev/random is something you need to do ! )